In a mesh network, a communication path may be configured between a start-point node and an end-point node via a desired route. This allows the mesh network to provide flexible and efficient operations.
Meanwhile, protection (or a redundancy configuration) is provided to enhance network reliability. That is, a protection path is configured for a work path. In this case, when a failure occurs in the work path, data is transmitted via the corresponding protection path.
Shared Mesh Protection (SMP) or Shared Mesh Restoration (SMR) is known as a method for providing a mesh network with protection. Shared Mesh Protection and Shared Mesh Restoration may hereinafter be collectively referred to as Shared Mesh Protection.
FIG. 1 is an example of Shared Mesh Protection. In the example depicted in FIG. 1, a path for transmitting data between nodes A and B and a path for transmitting data between nodes C and D are requested.
A work path W1 and a protection path P1 are configured between the nodes A and B. The protection path P1 passes nodes X and Y. A work path W2 and a protection path P2 are configured between the nodes C and D. The protection path P2 also passes the nodes X and Y. That is, the protection paths P1 and P2 overlap each other in a section between the nodes X and Y. A section of a line that is shared by a plurality of protection paths may hereinafter be referred to as a “shared section”.
In the network above, when a failure occurs in the work path W1, a channel between the nodes X and Y is used to achieve the protection path P1. Meanwhile, when a failure occurs in the work path W2, a channel between the nodes X and Y is used to achieve the protection path P2. That is, a plurality of paths share resources for a communication between the nodes X and Y (e.g., communication band). Thus, Shared Mesh Protection may provide redundancy while using communication resources efficiently.
For Shared Mesh Protection, ITU-T has prepared, for example, Recommendation 808.3. Studies of Shared Mesh Protection for an OTN (Optical Transport Network) are also ongoing.
A proposed related art is a transmission system which performs protection for node failures by using protection paths equipped by a shared node protection system for each transmission path on a network formed of a plurality of nodes (e.g., Japanese Laid-open Patent Publication No. 2007-110366). In addition, a method has been proposed for efficiently carrying out settings wherein the bandwidth sharing among protection paths is taken into account (e.g., Japanese Laid-open Patent Publication No. 2007-49573).
In recent years, networks with flexibility and expandability have been required. Hence, various types of traffic may possibly be present on a network.
Assume that, in the network depicted in FIG. 1, a path for transmitting ODU1 between the nodes A and B is requested and a path for transmitting ODU2 between the nodes C and D is requested. In this case, a protection path for transmitting ODU1 and a protection path for transmitting ODU2 need to be provided within a shared section X-Y.
However, a method for configuring a plurality of protection paths with different capacities in a shared section (e.g., the shared section X-Y in FIG. 1) has not been established for Shared Mesh protection. Hence, when a failure occurs in a work path, it may take a long time to recover traffic via a corresponding protection path. When, for example, a failure occurs in the work path W1, an instruction to configure a path for transmitting “ODU1” is reported to the nodes within the shared section (corresponding to the nodes X and Y and nodes provided between the nodes X and Y in FIG. 1) in order. The individual nodes reconfigure a hardware circuit in order in accordance with the received instruction. Thus, it may take more than 50 milliseconds before traffic is recovered. That is, in a network that needs to satisfy a strict condition on a time of recovery from a failure (e.g., 50 milliseconds or shorter), it is difficult to provide Shared Mesh Protection in which protection paths with different capacities share a channel.